In recent years, an electric car using an electric motor as a driving source and a so-called hybrid electric car using a combination of an electric motor and another driving source are in the actual use. On such an automobile, an electricity storage device for supplying electricity as energy to the electric motor is mounted. As the electricity storage device, a secondary battery represented by a nickel-cadmium battery, a nickel-hydrogen battery, a lithium-ion battery, and the like or a capacitor that can be repeatedly charged and discharged is used. The electricity storage device is housed in a case and mounted on a vehicle body as an electricity storage pack.
There is a battery carrier support structure for an electric car as disclosed in Japanese Patent Laying-Open No. 6-270694, wherein a front bracket is fixed to a rocker by a bolt on an upper face of a front portion of a flange of a battery carrier and a rear bracket is fixed to the rocker by a bolt on an upper face of a rear portion of the flange of the battery carrier. In the battery carrier support structure, a lower wall portion of a rocker inner is formed at its middle portion in a front-rear direction of the vehicle with a bent bead. A rear portion of the rocker bends downward from the bent bead as a bend. A sliding load of the front bolt is smaller than that of the rear bolt. According to this battery carrier support structure, an energy absorbing burden on a front side member can be reduced, when an impact force is applied from a front side of the vehicle body.
There is a battery mounting structure as disclosed in Japanese Patent Laying-Open No. 2004-262413, wherein a plurality of elongated holes are formed in stays to which the batteries are coupled and which fix the batteries onto a floor panel to thereby form brittle portions on the stays. In the brittle portions, the strength only in the front-rear direction is reduced to a certain degree while the strength in the vertical direction is maintained. In this battery mounting structure, if the spare tire at the front of the vehicle body is struck up while guided by a slope in a collision and collides with rear portions of the batteries, the stays are deformed at their brittle portions. With this battery mounting structure, it is possible to prevent damage to the batteries due to the collision of the spare tire struck up in the collision. In place of the elongated holes formed in the stays, elongated holes having open rear ends may be formed in flanges to form slide mechanisms.
There is a battery frame fixing portion structure as disclosed in Japanese Patent Laying-Open No. 7-81431, wherein a side frame of a battery frame is fixed by a bolt and a nut plate and a front slit portion and a rear slit portion are formed on a front side and a rear side of an insertion hole for the bolt of a side member. A reinforcing member is inserted into the side member from a position corresponding to a rear portion of the side frame to a rear end of the side member. A front end of the reinforcing member is fixed to the side member by inserting the bolt into the insertion hole. A slit is formed at a rear portion of the insertion hole of the reinforcing member. With this battery frame fixing structure for an electric car, it is possible to suppress increase in weight of a vehicle body to prevent movement of the battery frame in a collision.
There is a battery support structure for an electric car as disclosed in Japanese Patent Laying-Open No. 7-117490, wherein a mounting hole is formed in a flange of a battery carrier and a bolt is inserted through the mounting hole. The battery carrier is mounted to the rocker by the bolt with a specific tightening force. A thin-walled portion is formed on the flange of the battery carrier to be adjacent to the mounting hole. With this battery support structure, it is possible to absorb kinetic energy of the battery carrier as well as to improve rigidity of a supporting portion of the battery carrier supported on a vehicle body.
There is a battery support structure for an electric car as disclosed in Japanese Patent Laying-Open No. 6-115361, wherein a plurality of holes not communicating with each other are formed in a flange of a battery carrier along a front-rear direction of a vehicle body. With this battery support structure for the electric car, it is possible to improve rigidity of a support portion of the battery carrier supported on the vehicle body and also to absorb kinetic energy of the battery carrier.
The electricity storage pack is fixed to a support member such as a floor panel and a side member for supporting the electricity storage pack. Disclosed in the above-described Patent Documents is the structure for mounting the electricity storage pack on the vehicle and for absorbing an amount of the impact when the impact is applied from the front-rear direction of the vehicle body. In the above-described Patent Documents, the member supporting the electricity storage pack bends or the bolts inserted through the holes formed at intervals break the portions between the insertion holes to thereby absorb energy of the impact of the collision or the like.
Here, if a small car bumps into the rear of a standard-sized car, the support member for the electricity storage pack is deformed. The impact is applied on the electricity storage pack through the support member. In other words, a secondary impact is applied on the electricity storage pack due to deformation of the support member.
On the other hand, in a case of an impact from an outside high position, the impact may be directly applied on the electricity storage pack. For example, if the electricity storage pack is disposed on a floor of a trunk room of the standard-sized car and a large truck bumps into the rear of the car, the large truck may directly apply an impact on the electricity storage pack. In this case, the electricity storage pack itself may be broken by grinding or crushing. If the impact is applied from the outside high position, the electricity storage pack cannot be sufficiently protected.